Central lubricating system

ABSTRACT

A central lubricating system with at least a first and second distributing means each of which has cylinder means with reciprocable valve spools each having two end pistons and an intermediate control member. The control members of each distributing means control the admission of lubricant to areas to be lubricated. Conduit means lead from outlet means of the first distributing means to a control member controlled control chamber of the second distributing means. The conduit means establish the sole fluid communication of the last mentioned outlet means of the first distributing means with the control chamber of the second distributing means.

United States Patent [191 Kiirten et a1.

[ CENTRAL LUBRICATING SYSTEM [75] Inventors: Fritz Kin-ten, Dornap; Horst Saretzlty, Ennepetal, both of Germany [73] Assignee: De Limon Fluhme & (30.,

Dusseldorf, Germany [22] Filed: May 17, 1971 [21] Appl. No; 144,118

[52] US. Cl 184/7 E [51] Int. Cl. lFlfin 25/02 [58] Field of Search 184/7 R, 7 D, 7 E, 184/7 F; 137/271 [56] References Cited UNITED STATES PATENTS 2,986,234 5/1961 Akamatsu et al. 184/7 E 3,086,614 4/1963 Sensui et a1. 184/7 E 3,414,085 12/1968 Fujita 184/7 D FOREIGN PATENTS OR APPLICATIONS 787,478 12/1957 Great Britain 184/7 F 32 1 -11 I a ls 27 7: L730 19 22 *12 12 7 15 14 M 5 .11: l 16 1 28 l I Z 20 J n -29 5 1 14 H4 1 5 [111 3,783,973 1 Jan. 8, 1974 Primary ExaminerManuel A. Antonakas Att0rneyWalter Becker A central lubricating system with at least a first and second distributing means each of which has cylinder means with reciprocable valve spools each having two end pistons and an intermediate control member. The control members of each distributing means control the admission of lubricant to areas to be lubricated. Conduit means lead from outlet means of the first distributing means to a control member controlled control chamber of the second distributing means. The conduit means establish the sole fluid communication of the last mentioned outlet means of the first distributing means with the control chamber of the second distributing means.

10 Claims, 4 Drawing Figures PATENTED 81974 3.783.973

SHEET 2 OF 3 Fig.3

INVENTORS CENTRAL LUBRICATING SYSTEM The present invention relates to a central lubricating system with distributing elements comprising at least two double-acting pistons displaceable in a cylinder chamber between two end positions, according to which the cylinder chamber is subdivided into two working chambers and one control chamber while each piston has associated therewith a control valve which is adapted to open and close pressure conduits passing through control chambers. More specifically, the prese'nt invention concerns a central lubricating system of the above mentioned type which comprises an inlet conduit from which the pressure conduits are branched off and pass through the control chambers to a working chamber each in such a way that the pistons will successively, in conformity with a fixed cycle, press a lubricant into an outlet conduit and the valve associated with the respective piston will free a pressure conduit leading to a working chamber of a next following piston. Heretofore, two types of central lubricating systems were employed with preference, of which one type is known generally as a two-conduit system whereas the other type is usually termed progressive system.

A two-conduit system includes a lubricating pump and two feeding lines through which a lubricant is conveyed to a plurality of distributing elements. Each distributing element communicates with two feeding lines and comprises a plurality of double-acting pistons displaceable between two end positions. When subjecting the pistons to the feeding pressure of one feeding line, the pistons are displaced into the respective other end position while lubricant is pressed into the respective outlet conduits communicating with one piston side. Depending on the release of lubricant and the piston reaching its respective end position, the pressure will increase in this feeding line. A reversing device operating in conformity with the feeding line pressure shifts the lubricating pump over to the other feeding line so that the distributing elements are now supplied through the last mentioned feeding line with lubricant. This lubricating pressure is conveyed to the other side of the pistons in the distributing elements and displaces these pistons to their other end position while outlet conduits communicating with the other piston side are supplied with lubricant.

Such two-conduit system has a number of drawbacks. Such system requires many parts and is expensive, particularly also due to the fact that a reversing device is necessary. Moreover, it is very difficult in a twoconduit system to ascertain any possible clogging-up or blocking unless each individual piston of the distributing elements has a separate checking mechanism. The employment of so many parts becomes, however, uneconomical, particularly when a great number of points of lubrication are present. A clogging-up or blocking will in the same manner as a proper lubricating operation bring about an increase in pressure in the respective feeding line so that the reversing device will at any rate shift over to the other side of the feeding line without the clogging or blocking being noticed. Only a major leakage will prevent such increase in pressure and thus a shifting over of the reversing device to the other feeding line so that only then such disorder can be ascertained without a larger number of technical elements.

In a progressive system, only a single feeding line comes from a lubricating pump and leads to a progressively operating distributing element or through intermediate distributors to a plurality of such distributing elements. A progressively working distributing element is so designed that it comprises at least two double acting pistons displaceable between two end positions and arranged in a cylinder chamber. This cylinder chamber is subdivided into two working chambers and a control chamber while pressure conduits leading to the working chambers pass through the control chambers. The pistons have associated therewith control valves which free the pressure conduits or close the same in such a manner that the pistons will successively press lubricant in a fixed cycle into a respective outlet conduit. In this connection the control valve associated with this piston frees a pressure conduit leading to a Working chamber ofa next following piston. This cycle continues until the lubricating pressure prevailing at the inlet conduit of this distributing element is turned off. In conformity with the number of the points of lu brication to be supplied, these distributing elements may be provided with a different number of pistons and outlet conduits.

A progressive system requires considerably less technical parts than a two-conduit system, particularly inasmuch as the reversing device is not necessary. A clogging-up or blocking at any point of the central lubricating system results in an increase in pressure at the lubricating pump so that such disorder can easily be recognized. On the other hand, it is difficult to recognize any leakage, particularly in the main feeding lines to the distributing elements, without providing additional checking systems. While with a two-conduit system it is relatively simple to adapt the system to the respective requirement of the points of lubrication, such adaptation can at least to a major extent be carried out with a progressive installation only by changing the entire system. This is a rather important drawback inasmuch as frequently a simple adaptation to the respective requirement of the points of lubrication is necessary.

Based on the above situation, it is an object of the present invention to provide a central lubricating system which requires considerably less parts than a twoconduit system and is less expensive than a two-conduit system but is adaptable nevertheless in the same manner to the respective requirements of the points of lubrication.

It is another object of this invention to provide a central lubricating system as set forth in the preceding paragraph, which will make it possible easily to recognize any clogged-up or blocked areas without special checking mechanism.

These and other objects and advantages of the invention will appear-more clearly from the following specification in connection with the accompanying drawings, in which:

FIG. 1 illustrates a lubricating system according to the invention with two interconnected distributing elements, said system occupying a first operative position.

FIG. 2 shows the same system as disclosed in FIG. 1 but occupying a second operative position.

FIG. 3 shows the system of FIG. 1 in a third operative 'position.

FIG. 4 illustrates a central lubricating system according to the invention with three distributing elements.

3 The central lubricating system according to the present invention is characterized primarily in that between one of the outlet conduits of a first distributing element and one of the control chambers of a second distributing element there is connected a connecting line which represents the only feeding line leading into the control chamber.

The distributing elements of a central lubricating system according to the invention respectively operate by themselves in the manner of the distributing elements of a progressive system. However, whereas with progressive systems having a plurality of distributing elements, these elements are controlled and actuated by intermediate distributors, the connecting line arranged between two distributing elements and connected thereto provides a successive control so that each distributing element with its inlet conduit can be directly and fixedly connected to a supply conduit coming from the lubricating pump, and intermediate distributors become superfluous. Such a design results in a considerable decrease in the number of technical elements required. Moreover, the adaptability of flexibility of the central lubricating system is greatly improved because individual distributing elements can be replaced by different numbers of outlet conduits, and also entire distributing elements may be added or removed without necessitating the exchange of intermediate distributors.

In view of the connecting line provided in conformity with the present invention between two distributing elements, a successive control is provided inasmuch as each circulating cycle of a distributing element can be continued only when through the connecting line of the preceding distributing element per each circulating cycle there is at least once a lubricant conveyed, and when a following distributing element connected through a further distributing conduit will per each circulating cycle receive at least once a certain quantity of lubricant. Thus, if in one of the distributing elements a blockage occurs, preceding and following distributing elements can continue their cycle at best only until the connecting line to the adjacent distributing element must become effective. Such a system is easily checked. Major leakages in the connecting line and in the feeding line leading to the distributing elements have the same consequences. Thus, a relatively comprehensive control of the central lubricating system has been created.

If not only two distributing elements but also further distributing elements are provided for the central lubricating system, a further distributing conduit is also provided between the further distributing elements which further distributing conduit establishes communication between an outlet conduit of a distributing element and a control chamber of the next following distributing element and represents the only feeding line leading into this control chamber.

According to a further development of the invention, one of the pistons of one of the distributing elements is coupled to a contact switch which is interposed in a control and/or checking circuit of the central lubricating system. In this way it will be possible, for instance, to interrupt the lubricating operation for a certain period of time and to turn off the feeding pressure when all distributing elements have completed their cycle. If desired, also a timing mechanism may be provided by means of which the pump will be turned on again. Similarly, control and indicating elements may be provided.

The individual distributing elements of the central lubricating system may within a certain time period perform a different number of cycles which, according to a further suggestion of the invention, may be predetermined by interconnecting a plurality of outlets of a distributing element within or outside the same and by connecting these outlets to the control chamber of the next following distributing element through the intervention of connecting lines which represent the only supply means leading into the control chamber.

If only one single connecting line is provided, it is necessary through the latter to actuate the next following distributing element twice when the cycle of the next following distributing element is to be the same as the cycle of the preceding distributing element. This is due to the fact that the control chamber of a piston is acted upon twice during one cycle.

The setting of the cycles of the individual distributing elements need not necessarily be determined by the number of the connecting lines. According to a further development of the invention, it is also possible that the pistons and working chambers of interdependent distributing elements have different diameters and that the respective diameter is so selected that the quantities of lubricant respectively supplied during a working cycle are at an integral ratio with regard to each other and that the cycle of the distributing elements is determined by means of the different volume of lubricant supplied by a piston with each working stroke. If a connecting line is thus, for instance, connected to a working chamber which has a feeding volume twice as great as that of the remaining working chambers, this greater supply volume will suffice to actuate the control chamber of the next following distributing elements twice so that both distributing elements will have the same cycle. Between the two actuations, the preceding distributing element is blocked. Thus, there exists the possibility, in conformity with the setting of the respective cycle for the distributing elements, to cause individual points of lubrication to be supplied with a lubricant more frequently than other points of lubrication.

Referring now to the drawings in detail, a first distributing element 10 has three pistons 11, 12 and 13 each of which is displaceable between two end positions in a cylinder chamber composed of two working chambers 14 and 15 and a control chamber 16. The pistons 11, 12 and 13 have a central portion 11a, 12a and 13a, similar to a piston rod, of smaller cross section which each respectively forms part of the control chambers 16 and the central portion of which is provided with a control slide or valve 17. into each end of a control chamber 16 there leads one of the outlet conduits 18-23. Of the two outlet conduits 18 to 23 leading into one and the same control chamber, one conduit each is closed by the piston 11, 12, 13, whereas the other outlet conduit communicates with the control chamber 16. An inlet conduit 24 leads into the control chamber 16 of the lower piston 13. Conduit 24 communicates through a pressure line 25 with the control chamber 16 of the piston 12 and through a further pressure line 26 communicates with the control chamber 16 of piston 11. In this way lubricant is conveyed to all control chambers 16. In the vicinity of each outlet conduit 13-23, one of the pressure conduits 27-32 leads into the respective control chamber 16. The control valves 17 occupy relative to the conduits leading into the control chamber 16 such a position that in each end position of a piston 11, 12 or 13 one of the pressure conduits 27-32 and one of the outlet conduits 18-23 are separated from the lubricant supply effected through the pressure conduits 25, 26 and the inlet conduit 24. The other pressure conduits and outlet conduits communicate with the lubricant supply. The pressure conduits 27-32 respectively lead from a control chamber 16 to one of the working chambers 14, 15 in order to act upon the pistons 11, 12 and 13 in a certain direction.

A further distributing element 33 is designed similar to the distributing element 10. As far as the individual portions of the distributing element 33 carry out the same functions as those of the distributing element 10, they are designated with the same reference numerals. The important difference between the distributing element 10 and the distributing element 33 consists in that instead of the pressure conduit provided in the distributing element 10 and feeding the control chamber 16 of the piston 1 1, there is provided a pressure conduit 34 which leads into the control chamber 16 of piston 11. Connected to the pressure conduit 34 is 9. connecting line 35 which communicates with the outlet conduit 19 of the distributing element 10. Further material differences between the distributing elements 10 and 33 do not exist. A point of lubrication is connected to the outlet conduit 19 of the distributing element 33 similar to the provision of the other outlet conduits. The distributing elements 10 and 33 are built up in conformity with the building block principle. It will be evident that the number of the intermediate building elements may be varied in order to adapt the number of the outlet conduits to the respective requirements. Corresponding remarks also apply to the possible change of a distributing element in conformity with the distributing element 10 to obtain a distributing element corresponding to the distributing element 33.

In that region of the control chamber 16 into which the inlet conduit 24 and pressure conduits 25 and 26 lead there are provided annular passages not shown in the drawings. These annular passages serve the purpose of safeguarding an onflow of the lubricant also when the control valves 17 occupy a position in the connecting region of the said conduits. A connection of the control chambers 16 of pistons 11, 12 and 13 with the pressure conduits 25, 26 and the inlet conduit 24 can, however, also be effected through bores located outside the section plane illustrated, while the annular passages will in such an instance not be necessary.

The operation ofa central lubricating system according to the invention will now be described in connection with FIGS. 13.

In the operative position shown in FIG. 1, the pistons 11, 12 and 13 with their control slides 17 occupy such a position that lubricant can pass through the inlet conduit 24, pressure conduit 25, control chamber 16 of piston 12 and pressure conduit 30 into the working chamber 15 of piston 11. A displacement of pistons 12 and 13 can in this operative position not be effected because the working chambers 15 of pistons 12 and 13 which at the same time are exposed to the pressure of the lubricant are already filled. Thus, piston 11 of the distributing element 10, as indicated by an arrow, is moved toward the left. The lubricant will in this instance be pressed through pressure conduit 27, control chamber 16 of piston 12 and outlet conduit 19 into the connecting conduit 35.

At this time, the distributing element 33 occupies an operative position in which it is blocked as long as lubricant is not conveyed through the connecting conduit 35. This is due to the fact that the pistons 11, 12 and 13 of the distributing element 33 have reached a position of operation in which only the already filled working chambers 15 of pistons 11 and 12 are subjected to the pressure of the lubricant. The pressure of the lubricant is not conveyed to the working chamber 15 of piston 13. It is only the pressure of the lubricant coming from the connecting conduit 35 which acts upon the working chamber 14 of piston 13 and, more specifically, through control chamber 16 of piston 11 and pressure conduit 32. Thus, the distributing element 33 can receive the lubricant coming from the distributing element 10, and piston 11 of the distributing element 10 is able to move to its left-hand end position. Both distributing elements 10 and 33 are now able to continue the preset cycle and successively to act upon the next outlet conduits.

In the position of operation shown in FIG. 2, the pistons 11, 12 and 13 of the distributing element 10 occupy the same position as in the position of operation shown in FIG. 1. The piston 11 thus has the tendency through pressure conduit 27, control chamber 16 of piston 12 and outlet conduit 19 to convey lubricant into the connecting conduit 35.

However, pistons 12 and 13 of the distributing element 33 now occupy another position. The working chamber 14 of piston 13 is filled so that the piston 13 occupies its right-hand end position. It is for this reason that no further lubricant can be received through the right-hand portion of control chamber 16 of piston 11 and through the pressure conduit 32. The distributing element 10 can continue its cycle only when the working chamber 14 of piston 11 can be emptied through connecting conduit 35. Since this is not possible at this time, the distributing element 19 is blocked.

The distributing element 33 will carry out a cycle when acted upon by pressure through the connecting line 35. The distributing element 33 has, however, at this time not yet completed this cycle because in the illustrated position of operation the pressure of the lubricant is conveyed through the inlet conduit 24 via control chamber 16 of piston 13, through pressure conduit 25, through control chamber 16 of piston 12, and

through pressure conduit 27 into the working chamber 14 of piston 11 so that piston 11 will be moved to its right-hand end position. Lubricant is pressed through pressure conduit 30 and control chamber 16 of piston 12 into the outlet conduit 22. Control slide 17 of piston 11 establishes communication between the pressure conduit 34 and the working chamber 15 of piston 13 and, more specifically, via the left-hand portion of the control chamber 15 of piston 11 and through pressure conduit 31. Thus, piston 13 is moved into its left-hand end position while through pressure conduit 32 and the right-hand portion of control chamber 16 of piston 11 pressure is conveyed into the outlet conduit 21. Thus, the outlet conduit 19 of the distributing element 10 furnishes lubricant through the connecting conduit 25 so that the distributing element 10 is no longer blocked and now is able to continue its cycle.

In the position of operation shown in FIG. 3, the dis tributing element 33 is blocked because the distributing element 10 has not yet continued its cycle to such an extent that the outlet conduit 19 receives pressure. The

pistons l 1, 12 and 13 of the distributing element 33 Oecupy a position in which lubricant can pass to the working chamber 15 of piston 13 through pressure conduit 34, control chamber 16 of piston 1 1 and pressure conduit 31 so that an actuation of this piston is made possible. This actuation, however, does not take place yet because no lubricant is conveyed through the connecting conduit 35.

As will be evident from the illustrated position of operation of pistons ll, 12 and 13 including their control valves or slides 17, there will, as far as the distributing element is concerned, be obtained the situation that through pressure conduit 25, control chamber 16 of piston 12 and pressure conduit 30 lubricant pressure can be conveyed to the working chamber of piston 11. As a result thereof, piston 11 is displaced to its lefthand end position, and from the working chamber 14 of piston 11 lubricant is through pressure conduit 27, control chamber 16 of piston 12 and outlet conduit 19 conveyed to the distributing element 33 via connecting conduit 35. In the above described manner, the piston 13 of distributing element 33 is now moved to its lefthand end position so that also this distributing element is able to continue its cycle.

The central lubricating system shown in FIG. 4 has in addition to the distributing elements 10 and 33 a third distributing element 36 which communicates through a connecting conduit 37 with the outlet conduit 19 of the distributing element 33. The construction of the distributing element 36 is the same as that of the distributing element 33 so that the same reference numerals have been applied to the parts of this third distributing element 36.

The distributing element 36 represents serially the last distributing element of the annular lubricating system and is provided with a limit switch 38 which through a rod 39 connected with the piston 13. When lubricant is conveyed through pressure conduit 32 of the working chamber 14 of piston 13, piston 13 will be moved to its right-hand end position. At the same time, in the limit switch 38 there will be actuated a contact which engages a non-illustrated control system for a motordriven lubricating pump 40 which will then be stopped. As a result thereof, the operating pressure prevailing in a feeding line 41 leading to the inlet conduit 24 is switched off so that the distributing elements 10, 33 and 36 are stopped. The limit switch 38 or other control and checking elements may, of course, also be arranged on the distributing elements, on their pistons and on the piston sides in any desired manner.

Inasmuch as the distributing elements 10 and 33 in the arrangement shown in FIGS. 1 to 3 are connected with each other by a single connecting conduit 35 only, it will be appreciated, as far as the number of the cycles is concerned, that the distributing element 33 has half as great a cycle as the distributing element 10 so that with reference to the entire system, the points of lubrication connected to the distributing element 33 are lubricated half as often as those connected to the distributing element 10.

In the embodiment illustrated in FIG. 4, between the distributing elements 10 and 33 there are provided two connecting conduits 35 and 35a so that these distributing elements will have the same cycle. The cycle of the distributing element 36, on the other hand, is only half as great so that the points of lubrication connected thereto are lubricated correspondingly less often. More specifically, the following operation takes place.

Fundamentally, the dependency of the cycle of distributing element 33 on the supply of lubricant through the pressure conduit 34 remains. l-lowever, also the cycle of the distributing element 10 remains as before dependent on a supply of lubricant through the connecting conduit 35. If this supply is not possible, the distributing element 10 is blocked, and this dependency applies in the same manner for a supply of lubricant through the connecting conduit 35a which is connected to the outlet conduit 22 of the distributing element 10. The parallel arrangement of the outlet conduits l9 and 22 which can, of course, be effected also within the distributing element 10, at the entrance of the pressure conduit 34 of the distributing element 35 leads to a duplication of these dependencies. From this it will be evident that the distributing element 33 has adapted its cycle to thatof the distributing element 10 and that the points of lubrication connected to the distributing element 33 are supplied with lubricant as often as the points of lubrication connected to the distributing element 10.

In addition to the above, it is also possible to adapt the supply of the individual points of lubrication by means of another desired system of connecting conduits.

In the description of the above outlined embodiments it has always been assumed, for purposes of simplication, that the working chambers 14 and 15 and the pistons 11 to 13 are of the same size and that the pressure conduits have approximately the same cross sections so that approximately the same quantity of lubricant is conveyed to each point of lubrication. The requirement in lubricant of the individual points of lubrication to be met by a central lubricating system according to the invention may also be varied by having a plurality of outlet conduits lead to a single point of lubrication.

If, however, a piston and the working chambers associated therewith are designed with a diameter differing from the remaining working chambers and pistons, and if the size is so selected that the quantity of lubricant conveyed by this piston during a working cycle has an integral ratio with regard to the respective quantity of lubricant conveyed by another piston, it is also possible in this way to effect an adaptation of the cycles of two distributing elements independently of each other. In such an instance, the advantage is obtained that as before a single connecting conduit only is necessary and that at the respective preceding distributing element an outlet conduit for a further lubricating conduit becomes free inasmuch as the respective additional connecting conduit will be superfluous.

It is, of course, to be understood that the present invention is, by no means, limited to the particular embodiments shown in the drawings but also comprises any modifications within the scope of the appended claims.

What we claim is:

l. A central lubricating system which comprises in combination at least first distributing means and second distributing means, each of said distributing means including a plurality of cylinders and a plurality of valve spools respectively reciprocable in said cylinders, each of said valve spools having a piston at each end thereof and also having a control element arranged between and in axially spaced relationship to said pistons, each of said valve spools dividing the pertaining cylinder into two end chambers and a control chamber, each of said control chambers having passage means associated therewith for admitting lubricant to and discharging lubricant from the respective chamber, some of said passage means of each control chamber pertaining to one cylinder leading to the end chambers of another cylinder and others of said passage means of each control chamber ending in an outlet, some of said outlets being adapted to be connected to an area to be lubricated, each of said control elements being operable by lubricant under pressure conveyed to the respective end chamber of the respective cylinder to control the passage means associated with the pertaining control chamber so that the valve spools in predetermined cycles will feed lubricant successively to at least one of the pertaining outlets, inlet means for admitting lubricant under pressure into one of said control chambers, and connecting conduit means connecting one of said outlets of said first distributing means with passage means associated with a control chamber of said second distributing means, said connecting conduit means exclusively forming the only connecting conduit means solely ever for lubricating supply leading from said first distributing means into said last mentioned control chamber.

2. A central lubricating system in combination according to claim 1, which includes at least third distributing means of the type of said first and second distributing means, and additional connecting conduit means connecting one of the outlets of said second distribut' in g means with passage means associated with a control chamber independent of said third distributing means, said additional conduit means forming the only connecting conduit means leading from said second distributing means into said last mentioned control chamber.

3. A central lubricating system in combination according to claim 2, which includes switch means coupled to a valve spool of one of said distributing means, and also includes pump means operatively connected to said switch means to be controlled thereby, and conduit means connecting said pump means to said inlet means for conveying lubricant under pressure to said inlet means.

4. A central lubricating system in combination, according to claim 3, which includes conduit means interconnecting a plurality of said outlets of one of said distributing means and one conduit means being connected to a control chamber of another distributing means.

5. A central lubricating system in combination according to claim 4, in which interdependent distributing means respectively have different diameter cylinders and cooperating pistons, the diameters being such that the respective volumina of lubricant fed during a working stroke of the respective pistons are at an integral ratio with regard to each other, and the cycle of the distributing elements being set by the different lubricant volume fed by the respective piston during each working stoke thereof.

6. A lubrication system comprising, first and second distribution units, each unit including at least two double-acting pistons, each reciprocable within a cylinder chamber between two terminal positions, the cylinder chamber being divided into two working chambers for said pistons and one distribution chamber, each double-acting piston having an associated distribution slide valve in said distribution chamber for opening and closing conduits connected to the distribution chambers, an inlet conduit carrying lubricant under pressure leading to distribution chambers in the first unit and to all but one distribution chamber in the second unit, outlet conduits connected to said distribution chambers and discharging lubricant from said working chambers, pressure conduits from each distribution chamber to the working chambers of another cylinder chamber, said slide valves movable with said double-acting pistons opening said inlet conduit in each unit to the conduits to said working chambers successively and conduits from said working chambers to said outlet conduits successively, a pressure conduit connecting one outlet conduit in said first unit to the distribution chamber not connected to the inlet conduit in said second unit, so that the fluid under pressure from the one unit operates one of the pistons in the other unit.

7. A lubrication system as claimed in claim 6, comprising a third distribution unit, a further connecting pressure conduit extending between the outlet conduit of the second distribution unit and a distribution chamber in the third distribution unit and constituting the only feed conduit opening-into the said distribution chamber of the third distribution unit.

8. A lubrication system in combination as claimed in claim 6, in which one of the pistons in one of the distribution units is coupled to switch means of a control device for the lubrication system.

9. A lubrication system in combination as claimed in claim 6, in which several outlets of one distribution unit are connected to the distribution chambers of the following distribution unit by the corresponding said pressure conduits.

10. A lubrication system in combination as claimed in claim 6 in which the pistons and working chambers of interdependent distribution units differ in diameter, the diameters being such that the volumes of lubricant pumped at each working stroke bear a whole-number relationship to one another. 

1. A central lubricating system which comprises in combination at least first distributing means and second distributing means, each of said distributing means including a plurality of cylinders and a plurality of valve spools respectively reciprocable in said cylinders, each of said valve spools having a piston at each end thereof and also having a control element arranged between and in axially spaced relationship to said pistons, each of said valve spools dividing the pertaining cylinder into two end chambers and a control chamber, each of said control chambers having passage means associated therewith for admitting lubricant to and discharging lubricant from the respective chamber, some of said passage means of each control chamber pertaining to one cylinder leading to the end chambers of another cylinder and others of said passage means of each control chamber ending in an outlet, some of said outlets being adapted to be connected to an area to be lubricated, each of said control elements being operable by lubricant under pressure conveyed to the respective end chamber of the respective cylinder to control the passage means associated with the pertaining control chamber so that the valve spools in predetermined cycles will feed lubricant successively to at least one of the pertaining outlets, inlet means for admitting lubricant under pressure into one of said control chambers, and connecting conduit means connecting one of said outlets of said first distributing means with passage means associated with a control chamber of said second distributing means, said connecting conduit means exclusively forming the only connecting conduit means solely ever for lubricating supply leading from said first distributing means into said last mentioned control chamber.
 2. A central lubricating system in combination according to claim 1, which includes at least third distributing means of the type of said first and second distributing means, and additional connecting conduit means connecting one of the outlets of said second distributing means with passage means associated with a control chamber independent of said third distributing means, said additional conduit means forming the only connecting conduit means leading from said second distributing means into said last mentioned control chamber.
 3. A central lubricating system in combination according to claim 2, which includes switch means coupled to a valve spool of one of said distributing means, and also includes pump means operatively connected to said switch means to be controlled thereby, and conduit means connecting said pump means to said inlet means for conveying lubricant under pressure to said inlet means.
 4. A central lubricating system in combination, according to claim 3, which includes conduit means interconnecting a plurality of said outlets of one of said distributing means and one conduit means being connected to a control chamber of another distributing means.
 5. A central lubricating system in combination according to claim 4, in which interdependent distributing means respectively have different diameter cylinders and cooperating pistons, the diameters being such that the respective volumina of lubricant fed during a working stroke of the respective pistons are at an integral ratio with regard to each other, and the cycle of the Distributing elements being set by the different lubricant volume fed by the respective piston during each working stoke thereof.
 6. A lubrication system comprising, first and second distribution units, each unit including at least two double-acting pistons, each reciprocable within a cylinder chamber between two terminal positions, the cylinder chamber being divided into two working chambers for said pistons and one distribution chamber, each double-acting piston having an associated distribution slide valve in said distribution chamber for opening and closing conduits connected to the distribution chambers, an inlet conduit carrying lubricant under pressure leading to distribution chambers in the first unit and to all but one distribution chamber in the second unit, outlet conduits connected to said distribution chambers and discharging lubricant from said working chambers, pressure conduits from each distribution chamber to the working chambers of another cylinder chamber, said slide valves movable with said double-acting pistons opening said inlet conduit in each unit to the conduits to said working chambers successively and conduits from said working chambers to said outlet conduits successively, a pressure conduit connecting one outlet conduit in said first unit to the distribution chamber not connected to the inlet conduit in said second unit, so that the fluid under pressure from the one unit operates one of the pistons in the other unit.
 7. A lubrication system as claimed in claim 6, comprising a third distribution unit, a further connecting pressure conduit extending between the outlet conduit of the second distribution unit and a distribution chamber in the third distribution unit and constituting the only feed conduit opening into the said distribution chamber of the third distribution unit.
 8. A lubrication system in combination as claimed in claim 6, in which one of the pistons in one of the distribution units is coupled to switch means of a control device for the lubrication system.
 9. A lubrication system in combination as claimed in claim 6, in which several outlets of one distribution unit are connected to the distribution chambers of the following distribution unit by the corresponding said pressure conduits.
 10. A lubrication system in combination as claimed in claim 6 in which the pistons and working chambers of interdependent distribution units differ in diameter, the diameters being such that the volumes of lubricant pumped at each working stroke bear a whole-number relationship to one another. 